To the dismay of environmental groups, the Obama administration has told the U.S. Supreme Court that a global-warming suit by California and seven other states, seeking to require major power companies to reduce their greenhouse gas emissions, should be dismissed.

In papers filed with the court this week, Justice Department lawyers argued that the authority to curb emissions that cause climate change belongs to the Environmental Protection Agency - which has taken the first steps toward regulating greenhouse gases - and to Congress, where administration-backed legislation is stalled.

The Justice Department also contended that states should be barred from suing private companies for the harm their emissions allegedly cause within state borders. The government said judges have no clear standards for measuring that harm and deciding how to allocate the costs.

Power companies have already asked the court to dismiss the suit. The Obama administration also argued for dismissal but said the high court should wait until an appellate court addressed the issue.

Environmentalists and their allies were alarmed.

"This is the legal and political equivalent of unilateral disarmament," said Jonathan Zasloff, a UCLA law professor who writes about climate change litigation.

The lawsuit seeks court orders requiring power companies to reduce carbon dioxide emissions by 3 percent a year for 10 years, a tougher restriction than the EPA is proposing. Zasloff said the administration should use the suit as an incentive for companies to go along with federal regulations or climate legislation, but instead is siding with industry efforts to dismiss it.

"It's very disappointing," said Ken Alex, a senior assistant attorney general who represents California in the case.

He said the state agrees that global warming should be addressed by federal regulations rather than lawsuits, but "right now there is not a single control on any greenhouse gas emission from any power plant in the United States."

The suit was filed in 2004 by eight states, New York City and three land trusts. They argued that major coal-burning companies were contributing to climate change that damaged state resources.

None of the companies is based in California.

A federal judge in New York dismissed the suit, but an appeals court ruled in September that the states could try to prove their case.

In this week's filing, the Justice Department said the EPA has taken several steps to curb emissions, including a finding in December that greenhouse gases endanger the public health.

The agency is implementing rules limiting auto emissions over a five-year period and requiring new industrial plants to use improved pollution controls, government lawyers said.

The EPA's actions, authorized by Congress under the Clean Air Act, eliminate any legal basis for a state lawsuit, Justice Department lawyers said. They also argued that no state should be allowed to ask a federal judge to assess a problem as complex as global warming.